Approximately 50 soil scientists were brought together by Greg Henry to participate in the International Polar Year Project, Climate Change Effects on Canadian Arctic Tundra Ecosystems; Interdisciplinary and Multi-Scale Assessments. Our goal in this project was to provide an assessment of Canadian Arctic soils.
About half Canada has permafrost, permanently frozen soil, and this permafrost dramatically changes how soils, plants and animals respond and contribute to climate change. We are investigating how these soils differ from one another in their responses and why they differ. A key response is the storage of carbon because these permafrost soils hold 25% of the carbon sequestered in the terrestrial biosphere. As a group, we have explored how these soils store, release and process carbon. We knew that these carbon storage processes were controlled by nitrogen and thus, we also explored how nitrogen processing differed. Our work in 2008, highlighted the ultimate importance of water for these soils. Water affected how plants provided nitrogen to the soil; water affected how large organisms in the soil freed up this nitrogen and carbon for further storage and water affected how these soils released greenhouse gas back to the atmosphere. Most surprisingly, we found that soils that had little water were most susceptible to climate change. Our work highlighted that the vast desert that sits on the top of Canada, the Polar Desert, may be rapidly changing in response to climate change. The sustainability of this change is not yet known and we worry that many fragile Arctic soils, such as the dunes and deserts, may be under threat.
The nitrogen cycle, controls carbon sequestration. A key component of the nitrogen cycle in the Arctic is bryophytes which provide ammonia, which in turn is transformed to nitrate and used by plants. As expected, bryophytes were controlled by moisture and needed phosphorus for maximum efficiency. However, the normal organisms convert the nitrogen provided by bryophytes to a form available to the rest of the ecosystem, were absent. The organisms, autotrophic ammonia oxidizers, were found at very low levels across the Arctic. Instead, it appears that heterotrophic or archael ammonia oxidizers are the critical organisms in Canada’s Arctic. This is important because heterotrophic and archael oxidizers respond very rapidly to increases in temperature whereas autotrophic oxidizers do not. Thus, work in 2009 will focus on identifying what is the key group as this will be essential for predictions on how Arctic systems respond to climate change.
Most of Canada’s carbon is locked in the Arctic soils. A key activity in 2008 was the collection of samples we need to estimate the Arctic soil carbon storage and if it was declining or increasing over the last 20 years. This was a two step process, first we estimated soil carbon losses and/or gains over a long time period and then we estimated the variability associated with carbon storage in these soils. These results are currently being linked to the Canadian Soil Carbon project.
All of our research teams report the same dependency in Arctic systems. Response and contribution to climate change is highly dependent on plant species present in that soil. In other words, while moisture and temperature are important and have over the long term altered plant communities and soil types. Current responses are linked intimately to the plant present at the sampling location. As a group, we wish to highlight this observation as it suggests that invasive species in Arctic climes may have a significant influence on carbon cycling in Canada’s Arctic.